From the prospectus (March 2000 edition) entitled “Crane Construction Kit KBK classic and KBK ergo” of the firm Demag Cranes & Components GmbH, Wetter, Germany, there is known a crane construction kit system with C-shaped and I-shaped rails which are open at the bottom, by which one can implement different kinds of constructions, such as monorail telphers, single and double-beam overhead cranes. In each case, the rails are suspended from support structures, other rails, or traversing gears which run into other rails. These suspension systems consist essentially of a rod-like tension element, suspended from the aforesaid support structures, other rails or traversing gears, having at the lower end a steel ball head, which engages with a mating ball cup with plastic slide shells. The ball cup is fastened by a fixing device to the rail being suspended. This ball and socket bearing of the suspension system ensures that the rails align themselves and thus come into a state of equilibrium, i.e., no significant bending load occurs in the tension element.
In a suspension system of C-shaped rails open at the bottom, with a web broadening out toward the top and arranged at the top side of the rail, preferably a Y-shaped or T-shaped web, the fixing device includes two identical fixing parts. These fixing parts are formed as sheet metal parts such that, after being fitted together and held by screws, the broadening web of the rail is clamped in the lower region and the ball cup is accommodated in the upper region, while the tension element is passed through an opening.
This type of suspension system has been popular for many years and may be easily installed on any given portion of a rail, since the fixing parts are fitted together and tightened together by the screws to clamp against the rail.
Also known from the firm of Demag Cranes & Components GmbH, Wetter, Germany, is another suspension system for a C-shaped crane rail open at the bottom, with a web arranged on the top side of the rail and opening upward in a Y-shape. This suspension includes a tension element and a single-piece fixing device. The tension element has a tension rod and a lug, which is secured by its bore to a bolt, which runs in the lengthwise direction of the rail and is mounted in the fixing device. Thus, the tension element can swivel transversely to the rail. The tension element is rigid in and against the lengthwise direction of the rail. The staple-shaped fixing device can be shoved onto the web of the rail from one end and can be fastened by a screw at the desired suspension point on the rail. The screw is led through a bore in the web.
European patent application EP 0 860 394 A2 describes the fastening of a tension element with a ball head in a mating ball cup by a fixing device on a Y-shaped web of a rail. The fixing device may be one-piece. The ball head of the tension element is led from above through the appropriately dimensioned opening of the fixing device and then the two-piece ball cup will likewise be introduced through this opening from the side. Whether the fixing device is secured by further means to the Y-shaped web of the rail is not specified.
German patent application DE-A 51 096 288 shows a fixing device for suspending a rail from an I-shaped beam. This C-shaped fixing device, open on top, has two opposite and swiveling gripping arms which, after the fixing device is arranged underneath the web of the rail, are swiveled by their hook-like ends into a fixing position on the top side of the web. The gripping arms are each fixed by a screw in the fixing position. In particular, this type of fixing is distinguished by the ability to adjust the fixing system with regard to the I-shaped rail. Even in the fixing position of the gripping arms there is sufficient lateral play to adjust the screws and move the fixing device itself sideways in relation to the rail. This document does not take up the subject of preventing a collapse in connection with a failure of the screws.
Moreover, there is known from German patent DE 197 53 169 C2 a device for suspending a rail, especially a hollow rail open at the bottom, for an overhead crane. Here, the rail is also characterized by a Y-shaped web arranged on top, being enclosed by a C-shaped fixing device, which is suspended via a ball head and a tension element from an I-shaped rail. The fixing device between the ball head and the Y-shaped web is in two pieces and is joined together by two screws extending transversely to the rail and arranged one behind the other, looking in the lengthwise direction of the rail. Thus, the ball head is grasped by the two parts of the fixing device. A failure of the screws would result in a loosening of the fixing parts, thus releasing the ball head of the tension element.